1. Gene mutations

• Mutation


  A change/ alteration in the base sequence of DNA
• Substitution mutation

  • One or more base is changed/ swapped for a different one
  • Number of bases remains the same
  • No frameshift
  • Only results in the changing of one codon
  • Unlikely to cause a change - genetic code is degenerate
• Deletion mutation

  • One or more base is deleted/ removed from the sequence
  • Cause frameshift to the left
  • Could result in a different polypeptide chain and a non-functioning protein
• Addition mutation

  • One of more extra bases are added to the sequence
  • Impacts all subsequent codons - frameshift
  • All those altered codons could potentially code for a different amino acids
  • Resulting in a non-functioning protein
• Inversion mutation

  • A section of bases are reversed
  • They detach from the sequence and re-join inverted
  • Results in the production of different amino acids
• Duplication mutation

  • One base is duplicated more than once in the sequence
  • Causes frameshift to the right
  • A different sequence of amino acids are coded for
• Translocation mutation

  • A sequence of base is moved from one location
  • Section on one chromosome detaches and attaches to a different chromosome
  • Substantial alteration
  • Causes significant impact on gene expression and an individuals phenotype
• Mutation occur during

  DNA replication when the DNA is read wrong
• Examples of mutagenic agents

  • UV radiation
  • Ionising radiation
  • Carcinogens
• Ionising radiation examples

  • Alpha and beta particles
  • X-rays and gamma rays
• Impact of carcinogens

  • Chemicals which can alter the structure of DNA
  • Also interfere with transcription
  • These chemicals are found in tobacco smoke, peroxides and mustard gas